docs: def available_files(url):
          """ Extract and return urls for all available .tgz files. """
          req = requests.get(url)
  
          if req.status_code != 200:
              raise base.FailedDownloadException('Failed to download data (status {}) from {}!'.format(req.status_code,
                                                                                                       url))
  
          page_content = req.text
          link_pattern = re.compile(r'<a href="(.*?)">(.*?)</a>')
          available_files = []
  
          for match in link_pattern.findall(page_content):
              if match[0].endswith('.tgz'):
                  available_files.append(os.path.join(url, match[0]))
  
          return available_files